The overall objective of the research project is to delineate the genetic, cellular, and molecular basis of complement resistance in Gram negative bacteria. The studies conducted during the past year focused on plasmids and bacteriophage as carriers of genetic information that can confer complement resistance on E. coli. We will determine how complement resistance is brought about by the traT gene of R-100 and the iss gene of ColV, and by lambda and certain other bacteriophages. We will search for other plasmid-borne complement resistance genes, particularly in clinical isolates of E. coli, and we will initiate studies with E. coli Kl, a strain responsible for most neonatal and infant E. coli infections.